Particularly when printing on articles such as CDs, telephone cards and credit cards, very small batch sizes frequently have to be printed. Batch sizes of only several hundred CDs or telephone cards are not a rarity. The consequence of this is that a disproportionately great amount of time is required for converting the printing machine from one batch to the next. In addition, with the machines which are usually employed nowadays. The conversion operation in that situation, that is to say adjusting the printing mechanisms to the print image of the respective following batch, requires very well-trained operating personnel if a print image of high quality is to be produced. In that respect, it will be noted that the requirements in terms of print image quality are becoming increasingly strict.
EP 0 488 092 B1 discloses a screen printing machine for printing on material in web form, wherein register marks applied to the web material are monitored by means of a camera. The screen printing stencils are arranged to be adjustable and for that purpose they are provided with setting motors which are controllable by way of a computer in dependence on the positions of the register marks, detected by the camera. However, adjusting the screen printing stencils in dependence on the position of register marks on the material to be printed does not result in significantly making the operation of converting the printing machine easier. Furthermore the quality of print image which can be achieved therewith does not satisfy the requirements which are usually imposed in many cases nowadays.